New conditions

We used nested conditions to add a check to test to several winners with the same results. Such conditions work, but they make the code difficult to read.

Let’s look at a simple everyday example. You went to a store to get some milk. If there’s no milk in the store, but there is some kefir then you’ll buy it. If there is no kefir, you’ll have to get some yogurt. And if they’re out of yogurt, you’ll have to buy soy milk, although you do not really like it. The code with nested conditions will look like this:

var isMilk = false;
var isKefir = false;
var isYogurt = true;

if (isMilk) {
  console.log('Excellent! I’ll take some milk!');
} else {
  if (isKefir) {
    console.log ('Then I’ll take some kefir!');
  } else {
    if (isYogurt) {
      console.log ('Oh well! I’ll buy some yogurt!');
    } else {
      console.log ('Well, I’ll have to take soy milk!');
    }
  }
};

// Logs 'Oh well! I’ll buy some yogurt!' in the console

The code looks cumbersome, don’t you think? There is a more convenient way to write it: a chain of conditional structures. It works when it is necessary to check more than two conditions and complete the check if any of the conditions are triggered.

The syntax is familiar to you, only in the second and subsequent branches, if can be separated by space immediately after else, and then a new condition can be added. Then, if the first check is not performed, the program will check the condition in the next branch. If the condition is wrong there, the code will be checked further. At the end of the structure, you can add a branch with the standard else if none of the previous conditions are met.

With the chain of conditions, the code for a trip to the store will look like this:

var isMilk = false;
var isKefir = false;
var isYogurt = true;

if (isMilk) {
  console.log('Excellent! I’ll take some milk!');
} else if (isKefir) {
  console.log ('Then I’ll take some kefir!');
} else if (isYogurt) {
  console.log ('Oh well! I’ll buy some yogurt!');
} else {
  console.log ('Well, I’ll have to take some soy milk!');
}

// Logs 'Oh well! I’ll buy some yogurt!' in the console

This way the code looks neater and it is easy to read.

Use the chain of conditions in our code.